Radiographic and Clinical Adjacent Segment Disease After Posterior Instrumented Fusion for Traumatic Thoracolumbar and Lumbar Vertebral Fractures

Background: Adjacent segment disease (ASD) after spinal fusion is well described in degenerative cohorts, but its radiographic and clinical behavior after acute traumatic thoracolumbar fracture fusion remains incompletely defined. This study evaluated whether ASD after traumatic fusion represents an imaging finding alone or a clinically relevant recovery-limiting event. Methods: This retrospective study included 98 patients who underwent posterior instrumented thoracolumbar/lumbar fusion for acute traumatic vertebral fractures. Because urgent surgery precluded meaningful preoperative disability assessment, the 1-month postoperative Oswestry Disability Index (ODI) was used as an early post-treatment functional reference point. Radiographic ASD was defined by new or progressive adjacent-level disc degeneration, disc-space narrowing, translation, angular instability, or junctional kyphosis, whereas clinical ASD was defined strictly as revision-confirmed symptomatic adjacent pathology. Results: Radiographic ASD occurred in 54 patients (55.1%), whereas revision-confirmed clinical ASD occurred in 11 patients (11.2%). Proximal and distal involvement were observed in 39.8% and 36.7% of patients, respectively. ODI improved from 42.5 ± 15.4 at 1 month to 27.0 ± 10.9 at final follow-up. Radiographic ASD alone was not associated with worse functional recovery. In contrast, revision-confirmed clinical ASD identified patients with markedly reduced ODI improvement (4.4 ± 2.8 vs. 16.9 ± 17.0; p = 0.007), and no patient with revision-confirmed clinical ASD achieved the ODI minimum clinically important difference. Conclusions: ASD after traumatic fusion should be interpreted as a clinically stratified phenomenon: frequently radiographic, but clinically relevant primarily when revision-confirmed and associated with reduced ODI-based recovery.